Multiblade antenna



Sept. 21, 1965 Filed July 16, 1965 c. w. MlLEY 3,208,072

MULTIBLADE ANTENNA 5 Sheets-Sheet 1 L 1'- El INVENTOR.

IGVl/T Sept. 21, 1965 c. w. MILEY 3,208,072

MULTIBLADE ANTENNA Filed July 16, 1963 5 Sheets-Sheet 3 INVENTOR Sept. 21, 1965 c. w. MILEY 3,208,072

MULTIBLADE ANTENNA Filed July '16, 1963 5 Sheets-Sheet 4 INVENTOR. C41 Vl/V w- 7 BY Luv...

United States Patent 3,208,072 MULTIBLADE ANTENNA Calvin W. Miley, Fort Walton Beach, Fla., assignor to the United States of America as represented by the Secretary of the Air Force Filed July '16, 1963, Ser. No. 295,567 Claims. (Cl. 343895) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmetal pur poses without the payment to me of any royalty thereon.

This invention relates to a broad band multiblade antenna.

One object of the invention is to provide an antenna with a characteristic impedance of near 50 ohms over a broad band of frequencies.

Another object of the invention is to provide an antenna which tends to ease of design and fabrication.

Another object of the invention is to provide an antenna wherein the inner and outer curved surfaces are of circular shape and wherein a mere change in size is required when operation at other frequencies is desired.

A further object of the invention is to provide an antenna which is aerodynamically stable with a low silhouette.

These and other objects will be more fully understood from the following detailed description taken with the drawing wherein:

FIG. 1 is a perspective view of the two antennas of the invention connected to a commercially available 50 ohm power divider.

FIG. 2 is a side elevation view of one of the antenna elements of FIG. 1;

FIG. 3 is an end view of the antenna element of FIG. 2;

FIG. 4 is a top view of the side blade member before bending for the antenna of FIG. 2;

FIG. 5 is a side elevation view of the center blade of the device of FIG. 2;

FIG. 6 shows a field pattern of an azimuth cut of an antenna shown in FIG. 2;

FIG. 7 shows a field pattern of an elevation cut of an antenna shown in FIG. 2.

FIG. 8 shows the coordinate system used for the field patterns of FIGS. 6 and 7; and

FIG. 9 shows the curve for VSWR vs. Frequency for the antenna of the invention.

A broad band antenna with a 50 ohm characteristic impedance is needed for use on space probe vehicles, and such an antenna has to have good pattern coverage to the rear. For complete pattern coverage, two antennas, placed on opposite sides of the missile are required. Prior art antennas create a critical matching problem to achieve a low voltage standing wave ratio in matching the antennas to the transmitter and receiver through standard 50 ohm power divider and 50 ohm coaxial line. The multiblade antenna of the invention proved ideal for such an application since it provides broad bandwidth and a characteristic impedance of 50 ohms. This permits the use of commercially available 50 ohm power dividers and also eliminates the necessity of cutting cables to critical lengths. The antenna of the invention is shown with three semicircular blades with circular shaped cuts to simplify construction. The size of the inner cut with respect to the outer circular shape controls the bandwidth. Changes can be made in the center cut and outer circular size to vary the bandwidth.

Referring now to FIG. 1 of the drawing two antennas 11 and 12 are shown connected to a standard commercially available 50 ohm power divider 13. Each of the antennas 11 and 12 has the construction shown in FIG. 2.

32%,072 Patented Sept. 21, 1965 Each antenna has three semicircular shaped blades 16, 17 and 18 mounted on a conductive ground surface member 19. The blades 16, 17 and 18 have semicircular cutouts 21, 22 and 23 to control the bandwidth. Blades 16 and 17 are made from a single circular piece of metal 20, such as brass which is bent to provide approximately a 21 angle with respect to the ground plane. This angle gives the optimum pattern for beacon tracking of space probe vehicles but can be varied to correspond the desired pattern coverage as determined by the particular application of the antenna. A hole 26 is cut in the circular piece of metal thus leaving a broad edge portion 24 and a narrow edge portion 25 on each of the blades 16 and 17. The broad edge portion 24 of blades 16 and 17 is connected to member 19, at 27 for example, by means of silver soldering. The center blade 18 is approximately semicircularly shaped as shown in FIG. 5 and has an approximately semicircular cutout 23 therein. The narrow portion 28 of blade 18 is shorter than the broad portion 29 so that when the broad portion 29 is silver soldered to member 16 and 17 a space 30 is left between portion 28 of blade 18 and the portion 25 of blades 16 and 17. In the device shown this space is inch. However, this dimension will be determined by the size of the antenna and is selected to adjust the capacitive reactance to allow for a low VSWR. The center conductor feed shown schematically at 32 of coaxial line connected at 33 is connected to the narrow portion 25 of blades 16 and 17 through a hole 34 in member 19. While the antenna has been described as fed by a coaxial line it is obvious that a waveguide feed could be used as with the prior art scimitar antenna.

There is thus provided an antenna which lends itself to ease of design and fabrication and which provides a characteristic impedance of near ohms over a broad band of frequencies.

While certain specific embodiments have been described in detail it is obvious that numerous changes may be made without departing from the general principles and scope of the invention.

I claim:

1. An antenna comprising: means for forming a conductive ground surface; an antenna feed opening in said ground surface means; three substantially semicircular shaped antenna blades; a substantially semicircular shaped cut in each of said blades with the center of the radius of said cuts being displaced along the edge of said blades from the center of the radius of said blades, to thereby provide a larger edge on one side of said cut than on the other side in each blade; said larger edge, of each of said blades, being attached to and electrically connected to said ground surface means, with the plane of the center blade being substantially perpendicular to said ground surface means and the plane of the two side blades extending at equal angles to the plane of said ground surface means; said two side blades being electrically connected together and spaced from said ground surface means adjacent said feed opening, said center blade being spaced from said two side blades adjacent said feed opening, to thereby provide a capacitive gap between said center blade and said side blades.

2. An antenna comprising; means for forming a conductive ground surface; an antenna feed opening in said ground surface means; a circular shaped antenna element; a circular shaped hole cut in said antenna element having its center displaced from the center of said circular shaped element; said circular shaped antenna element being bent along a diameter through the center of said hole, said antenna element being electrically connected to said ground surface means along the bent portion remote from feed opening and electrically separated from said ground surface means adjacent said feed opening, to thereby provide two antenna blades projecting at predetermined equal angles from said ground surface means; a third antenna blade having a substantially semicircular shape located between said two antenna blades and electrically connected thereto at the portion remote from said feed; a circular cut in said third blade adjacent the hole in said circular shaped antenna element; said third blade being spaced from said circular shaped antenna element adjacent said feed opening, to thereby provide a capacitive gap between said third blade and said circular shaped antenna element.

3. An antenna comprising: means for forming a conductive ground surface; an antenna feed opening in said ground surface means; a circular shaped antenna element; a circular shaped hole cut in said antenna element having its center displaced from the center of said circular shaped element; and circular shaped antenna element being bent along a diameter through the center of said hole to thereby provide a large edge and a smaller edge on opposite sides of said hole; and two antenna blades projecting at predetermined equal angles from said ground surface means; a second antenna element having a substantially semicircular shape of equal radius to said circular shaped antenna element; a semicircular shaped cut in said third blade having its center of curvature displaced from the center of curvature of the third blade by a distance equal to the spacing in said circular shaped antenna element to thereby provide a large edge and a smaller edge on opposite sides of said cut; said larger edge of said second element and said larger edge of circular shaped antenna element being electrically connected to said ground surface means; said smaller edge of said circular shaped antenna element being spaced from said ground surface means, adjacent said feed opening said second antenna element being spaced from said circular shaped antenna element adjacent said feed opening to thereby provide a capacitive gap between said third blade and said circular shaped antenna element.

4. An antenna comprising: means for forming a conductive ground surface; a circular cut in said conductive ground surface means, to thereby provide an antenna feed; three substantially semicircular antenna blades projecting at different angles from said conductive ground 4- surface means, and each having one end thereof extending across the circular cut in the conductive ground surface means; a cut in each of said blades with one edge of the cut in each blade being located adjacent the circular cut in said ground surface means; each of said blades being attached to and electrically connected to said ground surface means, at a portion of the edge remote from said circular cut in said ground surface means; two of said blades being electrically connected to each other and electrically separated from said ground surface means at the edge thereof adjacent said circular cut in the ground surface means; the third of said three blades being located between and electrically connected to said two blades at the edge remote from said circular cut and being spaced from said two blades at the edge adjacent said circular cut to thereby provide a capacitive gap between said third 'blade and said two blades.

5. An antenna comprising means for forming a conductive ground surface, an antenna feed opening in said ground surface means; three substantially semicircular antenna blades projecting from said conductive ground surface means, each having one end thereof extending across the said feed opening; a substantially semicircular cut in each of said blades with one edge of the cut in each blade being located adjacent the feed opening and having its center of curvature displaced from the center of curvature of said antenna blades toward said feed opening; each of said blades being attached to and electrically connected to said ground surface means at a portion of the edge remote from said feed opening; two of said blades being electrically connected to each other and electrically separated from said ground surface means at the edge thereof adjacent said feed opening; said two blades forming equal angles with respect to said ground surface means, the third of said three blades being spaced from said two blades at the edge adjacent said feed opening to thereby provide a capacitive gap between said third blade and said two blades.

References Cited by the Examiner UNITED STATES PATENTS 3,015,101 12/61 Turner et al. 343-895 X HERMAN KARL SAALBACH, Primary Examiner. 

1. AN ANTENNA COMPRISING: MEANS FOR FORMING A CONDUCTIVE GROUND SURFACE; AN ANTENNA FEED OPENING IN SAID GROUND SURFACE MEANS; THREE SUBSTANTIALLY SEMICIRCULAR SHAPED ANTENNA BLADES; A SUBSTANTIALLY SEMICIRCULAR SHAPED CUT IN EACH OF SAID BLADES WITH THE CENTER OF THE RADIUS OF SAID CUTS BEING DISPLACED ALONG THE EDGE OF SAID BLADES FROM THE CENTER OF THE RADIUS OF SAID BLADES, TO THEREBY PROVIDE A LARGER EDGE ON ONE SIDE OF SAID SIDE CUT THAN ON THE BLADES, BEING ATTACHED TO AND ELECTRICALLY CONNECTED TO SAID BLADES, BEING ATTACHED TO AND ELECTRICALLY CONNECTED TO SAID GROUND SURFACE MEANS, WITH THE PLANE OF THE CENTER BLADE BEING SUBSTANTIALLY PERPENDICULAR TO SAID GROUND SURFACE MEANS AND THE PLANE OF THE TWO SIIDE BLADES EXTENDING AT EQUAL ANGLES TO TH EPLANE OF SAID GROUND SURFACE MEANS; SAID TWO SIDE BLADES BEING ELECTRICALLY CONNECTED TOGETHER AND SPACED FROM SAID GROUND SURFFACE MEANS ADJACENT SAID FEED OPENING, SAID CENTER BLADE BEING SPACED FROM SAID TWO SIDE BLADES ADJACENT SAID FEED OPENING, TO THEREBY PROVIDE A CAPACITIVE GAP BETWEEN SAID CENTER BLADE AND SAID SIDE BLADES. 